Thin-film solar cells based on hydrogenated amorphous silicon (a-Si:H) are a promising photovoltaic technology for delivering low-cost solar energy. They can be used for cost-effective applications, such as large area photovoltaic modules and cells on flexible substrates as well. The silicon is deposited at low temperatures (<200° C.) by using plasma-enhanced chemical vapor deposition (PECVD). This deposition technique is effective and enables the deposition on large area substrates with good uniformity. Moreover, deposition conducted at very low temperatures enables the utilization of many different types of substrates, such as metals, glass, plastics etc.
Unfortunately, the use of plasma inevitably affects the substrate material, often causing a diffused defect at the transparent front contact that increases recombination of light-generated charge carriers.